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PUC commissioners discuss Navigator's plume study models

The South Dakota PUC commission hears testimony regarding Navigator's application to build a carbon dioxide pipeline in South Dakota.

PUC commissioners are reviewing Navigator’s safety models as they consider the company’s application to build a CO2 pipeline.

Throughout the hearing for Navigator’s application process, all plume modeling data had been held in confidentiality. Navigator released parts of their safety plan for the first time this week.

Plume modeling is data that examines how carbon dioxide would disperse in the event of a pipeline rupture.

Matthew Frazell is a consultant with Environmental Resources Management Inc. He testified Thursday to the legitimacy of Navigator’s plume modeling.

Through the course of the hearing, three programs were identified as possible tools to conduct plume modeling. Navigator representatives pushed to show the reliability of a tool they used called PHAST.

Frazell said Navigator could be utilizing a more advanced tool known as CFD, or computational fluid dynamics, to be more exact in their plume modeling. He said for Navigator’s purposes, however, PHAST would be adequate.

“The use of computational fluid dynamics, from a dispersion modeling setting, a lot of people think it's going to be more accurate and going to give you the best answer. You can generally arrive at the same answer using PHAST as you would computational fluid dynamics,” said Frazell.

Kristie Fiegen is the PUC Chairperson. She questioned the reliability of PHAST modeling on South Dakota terrain.

“So there’s lots of rolling hills, lots of little creeks, and as you know, the weather in South Dakota changes minute by minute. The wind changes, the direction of the wind changes, I mean we have so much variation here. So the CFD model would be more valuable maybe in an area that has rolling hills and a lot of weather changes,” said Fiegen.

John Abraham, a professor of mechanical engineering at University of St. Thomas, testified on behalf attorneys representing landowners. He disagreed with Frazell on the reliability of PHAST modeling.

Abraham said CFD modeling would be far superior as PHAST modeling often under-predicts how far a plume would spread.

Frazell agreed with both Fiegen and Abraham that CFD would offer more detailed inputs but says PHAST plume modeling would serve Navigator’s purposes in the state.

PUC commissioners will hear testimony in Navigator’s application through Saturday.

Evan Walton is an SDPB reporter based in Sioux Falls. Evan holds a Master’s in English Literature from Southern New Hampshire University and was honorably discharged from the United States Army in 2015, where he served for five years as an infantryman.